Has anyone noticed that on the Samsung HTQ during the end of a DHW run at say 65 degC LWT the space heating will not start until the LWT sensor drops to around 50 degC. The pump is not running at the end of the DHW even though the 3 way valve is switched to space heating so the LWT temperature persists. The delay is 20 minutes or so and is a significant loss of heating time.
I expected the changeover from DHW to space heating to happen immediately but maybe this delay for cooling is a protection for any plastic UFH pipework fitted.
Is there a way to change this as my radiators are not restricted on temperature and would benefit from an instant changeover?
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The Gen 7 does something similar.
In my case I only heat the DHW to 50C, the circulating pump runs for 3 minutes every 10 minutes until the LWT drops to near the target LWT. This seems to take around 2 or 3 pumps runs in my case. I suspect the volumiser, which is on the return line, is still full of hot water so takes some time to clear it. The larger the volumiser, the longer this will take.
So changing the plumbing is the answer? Remove the Volumisers, move it the from the return to the flow or have DHW bypass it. I never understood why it is on the DHW circuit, doesn’t it mean the whole volume is wasted in the summer? For that reason and because I needed the space I removed mine.
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Thanks for the replies. No volumiser on mine it was a straight replacement for an oil boiler no plant room just using existing indirect tank. All works exceptionally well at 65degC heats up water in half an hour but Samsung HTQ has this safety lockout that waits until the LWT sensor temperature drops to 55degC before starting the space heating cycle. Just wondered if anyone who has one knows how to adjust it?
Just a long shot (the manual’s a pig) but what are your FSV#3021/2/3/4/5/6 settings?
There just might be a clue in the Installer’s Guide:
I’m wondering if the controller is using the #3023 setting (which should be for DHW restart only) for space heating restart…
Thanks Sarah
the settings are :
3021 55C
3022 2C
3023 5C
3024 5C
3025 90min
3026 4hr
My theory is that the controller has a 55 degC LWT safety lockout for space heating restart somewhere - maybe 3021?
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Worth trying raising it to 60.
Setting FSV 2091, 2092 or 2093 to “Water pump3” will fix this, this will ensure the pump keeps running for a bit at the end of a DHW cycle which will very quickly bring the LWT down which will result in the system switching back to space heating.
The choice of FSV 2091, 2092 or 2093 will depend on if you’re using an external thermostat or not, and if you’re using floor or FCU water law control.
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Thanks Glyn, in my case I use the remote controller room temperature control 2093 and this was set pump1. I have now changed it to pump3 and will see how that goes on the DHW heating cycle.
Changing to the pump3 setting worked a treat!
This is a great result as I can now heat my water tank with only 30 minutes loss of space heating. In that sense the DHW performance of the Samsung HTQ at 65C is exactly the same as the old oil burner it replaces. It means that a standard UK indirect 120 litre tank size can continue to suit most household hot water demands as it is easily replenished within 30 minutes as required.
Thanks again for all your help.
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